What Frequencies Are Legal to Use Without a License?

What Does Unlicensed Spectrum Mean?

The radio frequency spectrum is a finite resource managed by government agencies - the FCC in the United States, ETSI and national authorities in Europe, and equivalent bodies in other countries. Most of the useful spectrum is licensed: specific frequencies are assigned to specific users (cellular carriers, TV broadcasters, military, emergency services) who pay for exclusive or priority access.

Unlicensed spectrum is different. These are frequency bands where anyone can transmit without obtaining an individual license, provided their equipment meets the technical requirements (power limits, modulation rules, certification). The operator does not need permission. The device does need to be approved.

The concept is similar to public roads versus private driveways. Licensed spectrum is like a private road - only the licensee can use it. Unlicensed spectrum is like a public road - everyone can use it, but you still need a licensed vehicle (certified device) and must follow traffic rules (Part 15 or equivalent regulations).

Unlicensed spectrum powers the wireless technologies most people use daily: WiFi, Bluetooth, Zigbee, Z-Wave, LoRa, cordless phones, baby monitors, garage door openers, wireless keyboards, and countless IoT devices.

graph TD
    subgraph "Unlicensed Frequency Bands"
        A[Unlicensed Spectrum] --> B[900 MHz ISM - US Only]
        A --> C[2.4 GHz ISM - Global]
        A --> D[5 GHz U-NII - Most Countries]
        A --> E[5.8 GHz ISM]
        A --> F[6 GHz - WiFi 6E - Expanding]
        A --> G[60 GHz - Millimeter Wave]
        B --> H[LoRa, Zigbee 900, Garage Openers]
        C --> I[WiFi, Bluetooth, BLE, Zigbee]
        D --> J[WiFi 5 GHz, Radar Sharing]
        F --> K[WiFi 6E, WiFi 7]
        G --> L[WiGig, Short Range Links]
    end

Major unlicensed frequency bands and the technologies that use them

ISM Bands - The Original Unlicensed Spectrum

ISM stands for Industrial, Scientific, and Medical. These bands were originally allocated by the International Telecommunication Union (ITU) for non-communication purposes: industrial heating, medical diathermy equipment, and scientific instruments. Microwave ovens operate at 2.45 GHz because that frequency was allocated for industrial heating - WiFi came later and had to share.

The major ISM bands are:

6.765-6.795 MHz: Low-frequency ISM, used by induction heating equipment.

13.553-13.567 MHz: Used by RFID systems and induction heating.

26.957-27.283 MHz: Used by CB radio (licensed in some countries, unlicensed in others) and RC toys.

40.66-40.70 MHz: Limited use, some industrial applications.

433.05-434.79 MHz: Available in Region 1 (Europe, Africa). Used by key fobs, weather stations, and garage door openers in Europe.

902-928 MHz: Available in Region 2 (Americas) only. Used by LoRa, Zigbee 900, cordless phones, and garage door openers in the US.

2.400-2.4835 GHz: Global availability. The band that WiFi, Bluetooth, and Zigbee all share.

5.725-5.875 GHz: Global availability. Part of the 5 GHz WiFi ecosystem.

24.00-24.25 GHz: Used by vehicle radar and some point-to-point links.

The term "ISM band" is sometimes loosely used to describe any unlicensed band, but technically the ISM bands are specifically defined by the ITU. The U-NII bands at 5 GHz, for example, are unlicensed but are not ISM bands.

The 2.4 GHz Band - Most Congested Spectrum on Earth

The 2.4 GHz ISM band (2.400-2.4835 GHz) is arguably the most valuable and congested unlicensed spectrum in existence. It carries WiFi (802.11b/g/n/ax), Bluetooth and BLE, Zigbee (802.15.4), Thread, Matter (over Thread or WiFi), ANT+, some DECT cordless phones, wireless USB, and older wireless video transmitters.

The band is only 83.5 MHz wide. WiFi divides this into 14 channels (13 in most countries, 11 in the US), each 20 MHz wide with 5 MHz spacing. Only three channels (1, 6, and 11) do not overlap with each other. In dense environments - apartment buildings, office complexes, conference halls - every non-overlapping channel may be occupied by multiple access points.

Bluetooth uses frequency hopping across 79 channels within the same band, each 1 MHz wide. BLE uses 40 channels, each 2 MHz wide, with 3 advertising channels and 37 data channels.

The congestion problem is real. In a typical urban apartment, a WiFi scanner might detect 30-50 access points on the three non-overlapping channels. Add Bluetooth devices (keyboards, mice, headphones, speakers, smartwatches, fitness trackers), Zigbee smart home devices, and the neighbor's microwave oven, and the 2.4 GHz band becomes extremely crowded.

This congestion is why WiFi has expanded to 5 GHz and 6 GHz - not because those bands are technically superior for all use cases, but because the 2.4 GHz band simply ran out of room.

U-NII Bands - The 5 GHz Alternative

The Unlicensed National Information Infrastructure (U-NII) bands provide additional unlicensed spectrum at 5 GHz. Unlike the ISM bands, U-NII bands were specifically created for data communication, not repurposed from industrial use.

U-NII-1 (5.15-5.25 GHz): Four 20 MHz channels (36, 40, 44, 48). Originally indoor-only in the US, now permitted outdoors. No DFS required.

U-NII-2A (5.25-5.35 GHz): Four channels (52, 56, 60, 64). DFS required due to radar sharing. Devices must detect radar and vacate the channel.

U-NII-2C (5.47-5.725 GHz): Eleven channels (100-140). DFS required. This is the largest contiguous block in the 5 GHz range.

U-NII-3 (5.725-5.85 GHz): Five channels (149, 153, 157, 161, 165). Overlaps with the 5.8 GHz ISM band. Higher power allowed (4W EIRP in US). No DFS required.

Together, the U-NII bands provide 24 non-overlapping 20 MHz channels - compared to three at 2.4 GHz. With 40 MHz, 80 MHz, or 160 MHz channel widths (used by WiFi 5 and WiFi 6), the throughput potential is much higher than 2.4 GHz.

graph LR
    subgraph "5 GHz U-NII Bands"
        A[U-NII-1] -->|5.15-5.25 GHz| B[Ch 36-48 - No DFS]
        C[U-NII-2A] -->|5.25-5.35 GHz| D[Ch 52-64 - DFS Required]
        E[U-NII-2C] -->|5.47-5.725 GHz| F[Ch 100-140 - DFS Required]
        G[U-NII-3] -->|5.725-5.85 GHz| H[Ch 149-165 - No DFS]
        D -->|Radar Detected| I[Must Vacate in 200ms]
        F -->|Radar Detected| I
        I --> J[30 Min Cooling Period]
    end

U-NII sub-bands with DFS requirements for radar sharing

6 GHz - WiFi 6E and Beyond

The 6 GHz band (5.925-7.125 GHz) was opened for unlicensed use starting in 2020 (US) and is being adopted globally at different paces. It provides up to 1,200 MHz of new unlicensed spectrum - more than all existing 2.4 GHz and 5 GHz unlicensed spectrum combined.

WiFi 6E (802.11ax in 6 GHz) and WiFi 7 (802.11be) use this band. It supports up to seven 160 MHz channels or three 320 MHz channels (WiFi 7), enabling multi-gigabit wireless throughput.

The 6 GHz band uses different power categories:

Low Power Indoor (LPI): Higher power, but restricted to indoor use. Access points must have no external antenna connections to prevent outdoor deployment.

Very Low Power (VLP): Lower power, permitted for portable devices both indoor and outdoor.

Standard Power: Higher power outdoor operation, but requires Automated Frequency Coordination (AFC) to avoid interfering with incumbent licensed services in the band.

The 6 GHz band is still in the early stages of adoption. Not all countries have opened it for unlicensed use, and those that have may allow only a portion of the full 1,200 MHz.

The 900 MHz Band

The 902-928 MHz ISM band is available in the Americas (ITU Region 2) but not in Europe or most of Asia, where these frequencies are allocated to cellular or other licensed services.

This band is valuable for long-range, low-data-rate applications because lower frequencies propagate farther and penetrate buildings better than higher frequencies. Technologies using this band include:

LoRa/LoRaWAN: Long-range, low-power IoT protocol. Can achieve ranges of several kilometers with very low data rates (under 50 kbps).

Zigbee 900 (802.15.4g): Smart utility network protocol for metering and grid monitoring.

Z-Wave (908.42 MHz in US): Smart home protocol for locks, sensors, and switches.

Garage door openers: Traditional fixed-code and rolling-code systems.

In Europe, the equivalent for long-range IoT is the 868 MHz band (863-870 MHz), which has different power limits and duty cycle restrictions.

60 GHz - Millimeter Wave

The 57-71 GHz band is available for unlicensed use globally. These extremely high frequencies (millimeter wave) offer enormous bandwidth - up to 14 GHz of unlicensed spectrum. The tradeoff is very short range and inability to penetrate walls.

Technologies using 60 GHz include WiGig (802.11ad and 802.11ay) for multi-gigabit wireless links over short distances (typically under 10 meters). Use cases include wireless display connections, cable replacement, and high-speed data transfer between nearby devices.

The short range is actually an advantage for spectrum reuse - two 60 GHz links in adjacent rooms will not interfere with each other because the walls block the signals completely.

Where the BLEShark Nano Operates

The BLEShark Nano operates exclusively in the 2.4 GHz ISM band. Its ESP32-C3 chip supports both WiFi (802.11b/g/n) and Bluetooth Low Energy 5.0, both of which use the 2.400-2.4835 GHz range.

This single-band operation means the BLEShark Nano can scan and interact with WiFi networks on channels 1-14 (channels 1-11 in the US, 1-13 in most other countries, 1-14 in Japan only) and BLE devices on all 40 BLE channels within the same band.

The 2.4 GHz band's global availability is an advantage - the same hardware works in any country. Power limits and allowed features may differ by region (handled through firmware), but the frequency band itself is universally available for unlicensed use.

Conclusion

Unlicensed spectrum spans from 900 MHz to 71 GHz, with the 2.4 GHz and 5 GHz bands carrying the vast majority of consumer wireless traffic. Each band has its own characteristics: 900 MHz for range, 2.4 GHz for universal compatibility, 5 GHz for capacity, 6 GHz for next-generation throughput, and 60 GHz for extreme short-range bandwidth.

The BLEShark Nano's focus on the 2.4 GHz band gives it access to the most widely used unlicensed spectrum globally - the band where WiFi, Bluetooth, and numerous IoT protocols all coexist and compete for airtime.